System and method for optimizing transferred fluid volume during an oil well pumping cycle

ABSTRACT

A system and method for optimizing transferred fluid volume during an oil well pumping cycle. The speed of a traveling valve, which lifts the petroleum from the well, is monitored to determine at what point during its downstroke the traveling valve contacts the hydrocarbon fluid that has accumulated in the bottom of a petroleum pipe. The system then analyzes speed data returned by a lift sensor and adjusts the speed of the traveling valve either upward or downward during the next upstroke to optimize the amount of hydrocarbon fluid transferred. The system can be configured to handle different ascent speeds, and chooses the most suitable speed depending on the petroleum level detected within the production pipe during the route of the traveling valve downwards.

REFERENCE TO A RELATED APPLICATION

This is a non-provisional application relating to the content of, and claiming priority to, Mexican Patent Application No. NL/a/2005/000053, filed Jun. 22, 2005, which is incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention.

The present invention relates to the field of crude oil production and, more specifically, to a system and method for optimizing transferred fluid volume by a traveling valve during a pumping cycle.

2. Background of the Invention.

In its broadest definition, an oil well is a perforation into the earth aimed to producing hydrocarbon liquids and gases. The life of a well typically has four stages: drilling, completion, production, and abandonment. The well is created by using a rig that turns a drill bit to drill into the earth. A casing pipe slightly smaller than the drilled hole is then run into the hole and cemented thereto. This casing provides structural support for the hole, which is subjected to a number of violent compressive forces and caustic chemicals during the drilling process. The casing also serves to isolate potentially dangerous high pressure zones from each other and from the surface. Wells frequently have multiple sets of progressively smaller hole sizes nested inside one another, each cemented with casing.

After drilling, the well is “completed,” which means that well is made capable of producing hydrocarbon products. In cased well bores, a section of the casing in the hydrocarbon producing zone is often perforated to allow the oil and gas to flow into the well bore from the surrounding formation. When a hole is not cased, which is called an open hole completion, a filter material such as sand or gravel may be used with the hole to facilitate the flow of oil and gas into the hole.

After completion, the drilling and completion tools are removed from the drill site, and the production tubing is connected to a collection of valves for regulating pressure and flow. This network of valves, sometimes called a “Christmas tree,” allows the hydrocarbons to be routed in a plethora of directions that may lead to different pipelines for moving the product off site.

Ideally, the well will produce hydrocarbons for a very long time, but inevitably, during the abandonment phase of the well's life, it becomes uneconomical to produce from the well. In most wells, the natural pressure of the subsurface reservoir is high enough to push the oil or gas to the surface, but this is not always the case. In depleted fields, such as fields with a high density of wells that causes the overall pressure to be widely disbursed, decreasing the production tubing diameter may be enough to help the production, but other types of artificial lift might also be used, such as downhole pumps or surface pumpjacks.

Real time monitoring of the upstroke and downstroke of an oil well is not new, but the primary focus of such applications have been directed toward minimizing or eliminating conditions known as “pump off” and “fluid pound.” See, e.g., U.S. Pat. No. 4,594,665; U.S. Pat. No. 4,666,375. Pump off occurs in depleted wells when fluid is withdrawn from the well at a rate greater than the rate at which fluid enters the well from the formation. In other words, the upstroke of the pump is removing the oil faster than the oil is produced by the formation. When pump off occurs, the subsequent down strokes begin to pound the fluid in the well, which causes severe jarring of the entire pumping unit potentially resulting in damage to the well equipment.

Other methods are directed primarily toward increasing the efficiency of the well. For example, U.S. Pat. No. 6,854,518 discloses a method for enhancing production of oil that reduces the pressure at the top of the well. The resulting increased difference between the well pressure at the surface and the well pressure at the formation results in a higher production flow.

U.S. Pat. No. 5,064,349 addresses both the pump-off and optimization problems by providing a method that includes measuring the displacement and the load on a rod string, determining when the well is pumped off due to stoppage of fluid flow, and subsequently adjusting the delay between each pumping cycle, meaning one upstroke and one downstroke. The delay time between cycles is determined from measuring the rod load during the downstroke until the rod load reaches a point of substantial stabilization.

Similarly, U.S. Pat. No. 6,497,281 also addresses both the pump-off and optimization problems by providing a “smart pump” that adjusts the rate of the well's pumping cycle to coincide with the well's production history. The invention uses stored production data to time the cycle appropriately for the rate of fluid produced from the formation.

In contrast to the prior art, the present invention optimizes the volume of hydrocarbons transferred during the upstroke of the pumping cycle. This allows a well operator to recover hydrocarbons from wells from which production would otherwise not be economically viable.

SUMMARY OF THE INVENTION

The present invention provides a method and system for optimizing the amount of fluid transferred during the upstroke of a pumping cycle. The system comprises a casing pipe. disposed in the ground and extending from the surface of the well to beneath a hydrocarbon production zone. The casing pipe has a perforated section for permitting petroleum to flow into the casing pipe from the surrounding hydrocarbon production zone. According to the preferred embodiment of the invention, a filtering material surrounds the casing pipe from the bottom of the well to a level above the production zone, thus requires any hydrocarbons flowing into the casing pipe to move through this filtering material. Concrete encircles the remainder of the casing pipe from the level of the filtering material to the surface.

A production pipe is nested within the casing pipe, and the production pipe further contains a system of valves for moving accumulated petroleum from the bottom to the top of the production pipe. As hydrocarbon fluid flows into the casing pipe through the perforated section thereof, the fluid accumulates at the bottom of the casing and production pipes. The valve assemblies, which are similar to ball-and-seat valves commonly used in the industry, operate to lift the hydrocarbon fluid from the bottom to the top of the production pipe, where it is forced though a first pipe and into a collection reservoir for later retrieval.

According to the preferred embodiment of the invention, the valve assemblies are functionally connected to a lift assembly located at the surface over the well. The lift assembly comprises a hydraulic lift moveable along a vertical axis that is parallel to the longitudinal axis of a pumping rod attached to a traveling, or moving, valve and a lift anchor affixed to the hydraulic lift. This assembly also includes a lift tower for providing the hydraulic lift with structural support and guidance for the movement of the hydraulic lift and a lift controller functionally connected to the hydraulic lift for controlling the valves according to a predefined program. A lift sensor measures the speed of the hydraulic lift and returns this speed measurement to the lift controller.

According to the method of the invention, the speed of the traveling valve is monitored to determine at what point during its downstroke the traveling valve contacts the hydrocarbon fluid that has accumulated in the bottom of the petroleum pipe. The system then analyzes speed data returned by the lift sensor and adjusts the speed of the traveling valve either upward or downward during the upstroke to optimize the amount of hydrocarbon fluid transferred. The system can be configured to handle different ascent speeds, and chooses the most suitable speed depending on the petroleum level detected within the production pipe during the route of the traveling valve downwards.

In the preferred embodiment, the operation of the fixed, traveling, and main valves generally apply typical ball-and-seat valve principles. A ball-and-seat valve is a device used to restrict fluid flow to one direction. It consists of a polished sphere, or ball, usually of metal, and an annular piece—the seat—that is ground and polished to form a seal with the surface of the ball. Gravitational force or the force of a spring holds the ball against the seat. Flow in the direction of the force is prevented, while flow in the opposite direction overcomes the force and unseats the ball. A more detailed description of this ball-and-seat operation as it pertains to the present invention is included herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention, as well as further objects and features thereof, is more clearly and fully set forth in the following description of the preferred embodiment, which should be read with reference to the accompanying drawings, wherein:

FIG. 1 describes operation of the system of the present invention; and

FIG. 2 describes the pump assembly positioned within a production pipe of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As shown in FIG. 1, the system of the present invention may be installed in a hydrocarbon producing zone 3 by drilling a vertical borehole 2 through the earth's surface 1 to determine the depth of the producing zone 3. Thereafter, the borehole 2 is further extended under the producing zone 3 and a casing pipe 4 disposed therein. Filtering material 5 is interposed between the casing pipe 4 and the wall and floor of the borehole 2. The filtering material 5 fills the space between the casing pipe 4 and borehole until a depth at least sufficient to span the producing zone 3. Concrete 6 fills the remaining space between the casing pipe 4 and borehole 2 wall above the filtering material 5.

The casing pipe 4 comprises a perforated section (not shown) positioned at the depth of the producing zone 3 for providing an ingress path for petroleum 50 that migrates through the filtering material 5. Petroleum 50 may be forced to the top of the casing pipe 4 by natural well pressure, where the petroleum 50 can flow through a casing unloading pipe 7 to a collection reservoir 8 for storage and later retrieval.

A production pipe 52 positioned within the casing pipe 4 extends from the bottom 10 of the casing pipe 4 to above the surface 1. By operating the system, petroleum 50 lifted to a production unloading pipe 11, which is interposed between the production pipe 52 and the collection reservoir 8, flows into the collection reservoir 8 for storage and later retrieval. Petroleum 50 is moved to a position where it may flow through the production unloading pipe 11 by a pump assembly 9 substantially contained within the production pipe 52 and operably attached to a lift assembly 54, the operation of which is described hereinafter.

A structure 12 affixed to the surface 1 over the casing pipe 4 provides support for the lift system 54, which drives the pump assembly 9. The pump assembly 9 is operably connected to a lift anchor 14 through the pumping rod 16. The lift anchor 14, in turn, is affixed to a hydraulic lift 13 partially housed within a lift tower 15, which provides guidance and support for the hydraulic lift 13 during operation. The hydraulic lift 13 vertically moves the lift anchor 14 along the lift tower 15 to cause the attached pumping rod 16 to drive a traveling valve 17 of the pump assembly 9, the operation of which is more thoroughly shown in FIG. 2. Centering bushings 18 are fixed within the production pipe 52 to guide movement of the pumping rod 16 and maintain a centered position thereof within the production pipe 52.

A lift sensor 20 returns the speed and position of the lift anchor 14 to a lift controller 19. Using the received speed and position information of the lift anchor 14, the lift controller 19 determines the position of the lift anchor 14 during a downstroke thereof when the traveling valve 17 encounters petroleum 50 within the production pipe 52. When the downward movement of the traveling valve 17 is impeded by petroleum 50, this resistance is detected by the lift sensor 20 from the speed reduction of the lift anchor 14, and the level of petroleum can be calculated. Based on the petroleum level within the production pipe 52, the lift controller 19 adjusts the speed (if needed) of the anchor 14 during the subsequent upstroke to ensure that the greatest possible volume of petroleum 50 is transferred. The greater the amount of petroleum to be transferred, the faster the anchor 14 must move the pumping rod 16 and traveling valve 17. The lift controller 19 is configurable to handle different upstroke speeds, from which the controller 19 will choose the most suitable speed depending on the level of petroleum 50 detected within the production pipe 52.

The pump assembly 9 comprises a main valve 21 fixed to the production pipe 52 near or at the bottom thereof. As more thoroughly shown by FIG. 2, the main valve 21 comprises a metallic main sphere 22 and a metallic main cone 23 having an opened base attached to the production pipe 52 at the circumference thereof and an opened apex of smaller diameter than the main sphere 22. The apex of the main cone 21 is oriented toward the bottom 10 of the production pipe to allow the main sphere 22 to rest therein. The opened base of a grid code 24 is affixed to the base of the main cone 21 with the apex of the grid cone 24 oriented toward the surface 1 to contain the main sphere 22 therebetween and facilitate the operation of the main valve 21. To optimize sealability of the main valve 21 and prevent the flow of petroleum 50 from above the main sphere 22 down through the main cone 23, the main sphere 22 and the main cone 23 are coated with a sealing liquid sprayed on the valve through a washing hose 25. As petroleum 50 moves from the producing zone 3 through the filtering material 5 and into the casing pipe 4, the accumulation of petroleum 50 causes the level of petroleum to raise and unseat the main sphere 22 from the apex of the metallic first cone 23 so the petroleum may move therethough.

The traveling valve 17, which is attached to the pumping rod 16 and moved by the upstroke and downstroke thereof, collects the petroleum 50 that has moved through the main valve 21 and raises the petroleum 50 to and through a fixed valve 26. Disposed in the traveling valve 17 are a four traveling cones 28 and traveling spheres 32 that function similarly to the main cone 23 and main sphere 22 described hereinabove, although alternative embodiments of the invention may have more or fewer of these traveling cones 28 and traveling spheres 32. The traveling cones 28 each have an opened base and an opened apex to allow petroleum communication therethrough. In addition, because the traveling valve 17 moves vertically within the production pipe 52, the side of the traveling valve is coating with a friction reducing material 27 (shown in FIG. 1).

As the traveling valve 17 encounters petroleum 50 in the production pipe 52 that has already moved through the main valve 21, the petroleum 50 is channeled through the opened bases of the traveling cones 28 to contact the traveling spheres 32 seated on the open apexes. This causes the traveling spheres 32 to lift, thereby allowing the petroleum to flow through the apexes to a position above the traveling valve 17. The transfer process is further facilitated by injecting a liquid flow enhancer (not shown) from the surface through a flow enhancer hose 29. As the traveling valve 17 initiates an upstroke, the traveling spheres 32 descend by the weight of the petroleum 50 to seal and seat against the apexes of the traveling cones 28, thereby impeding the exit of transferred petroleum 50 back through the traveling valve 17. As the traveling valve 17 moves to complete the upstroke, it pushes the collected petroleum 50 through a fixed valve 26, which also has a plurality of fixed spheres 33 seated on apexes of fixed cones 30 to prevent the petroleum 50 from flowing back through the fixed valve 26 in a downward direction. The fixed spheres 33 are unseated from the apexes of the fixed cones 30 when the petroleum is forced though the bases thereof, then are reseated when the traveling valve 17 initiates its next downstroke.

The petroleum 50 moved through the fixed valve 26 is pushed upwards by each upstroke of the traveling valve 17 until the level of accumulated petroleum reaches the production unloading pipe 11, by which the accumulated petroleum will flow through the production unloading pipe 11 to the collection reservoir 8 for storage and later collection.

The present invention is described in terms of a preferred illustrative embodiment in which a specifically described system is described. Those skilled in the art will recognize that alternative embodiments can be used when carrying out the present invention. Other aspects and advantages of the present invention may be obtained from a study of this disclosure and the drawings, along with the appended claims. 

1. A method for optimizing transferred fluid volume during an oil well pumping cycle having an upstroke and a downstroke, said method comprising: calculating the amount of petroleum that has been communicated through the traveling valve during said downstroke of said pumping cycle; and adjusting the speed of said traveling valve during the upstroke of said pumping cycle.
 2. A method for optimizing transferred fluid volume, as recited in claim 1, wherein said calculating step further comprises: receiving the speed of a lift anchor driving said traveling valve throughout said downstroke; analyzing changes of speed of said lift anchor to determine the level of hydrocarbon fluid present in said well; and determining a desired speed of said lift anchor for transferring an optimal amount of petroleum during next the upstroke.
 3. A system for optimally removing hydrocarbon fluid from a well comprising: a casing pipe extending from the surface of said well to beneath a hydrocarbon production zone and having a perforated section for permitting petroleum ingression into said casing pipe from said hydrocarbon production zone; a filtering material surrounding said perforated section of said casing pipe; a production pipe nested within said casing pipe; a pump assembly for transferring said hydrocarbon fluid upwell; and a lift assembly attached to said pump assembly for causing pumping action thereof.
 4. A system for optimally removing hydrocarbon fluid from a well, as recited in claim 3, wherein said pump assembly comprises: a main valve for allowing fluid communication only in an upwell direction, said main valve being affixed to said production pipe; a fixed valve positioned upwell from said main valve and attached to said production pipe, said fixed valve allowing fluid communication only in an upwell direction; a traveling valve interposed between said main valve and said fixed valve for transferring hydrocarbon fluid in an upwell direction during an upstroke of a pumping cycle; and a pumping rod having a first end affixed to said traveling valve and a second end affixed to said lift assembly, the longitudinal axis of said pumping rod being parallel to the longitudinal axis of said production pipe.
 5. A system for removing hydrocarbon liquid from a well, as recited in claim 3, said lift assembly comprising: a hydraulic lift moveable along a vertical axis that is parallel to the longitudinal axis of said pumping rod; a lift anchor affixed to said hydraulic lift to be moveable therewith and affixed to said pumping rod to move said pumping rod upward and downward; a lift tower for providing said hydraulic lift with structural support and guidance for the movement of said hydraulic lift, said lift tower being positioned relative to said pumping rod for attachment of said lift anchor to said pumping rod; a lift controller functionally connected to said hydraulic lift for controlling the velocity thereof according to a predefined program; and a lift sensor for measuring the speed of said hydraulic lift, said pumping rod, or said traveling valve, said lift sensor being functionally connected to said lift controller for communicating said speed measurement thereto.
 6. A system for removing hydrocarbon liquid from a well, as recited in claim 5, wherein said predefined program applies the method of claim 1 for optimizing the amount of hydrocarbon fluid transferred during an upstroke of a pumping cycle.
 7. A system for removing hydrocarbon liquid from a well, as recited in claim 5, wherein said predefined program applies the method of claim 2 for optimizing the amount of hydrocarbon fluid transferred during an upstroke of a pumping cycle.
 8. A system for optimally removing hydrocarbon liquid from a well, as recited in claim 5, wherein said hydraulic controller is configurable to move said hydraulic lift at different velocities.
 9. A system for optimally removing hydrocarbon liquid from a well, as recited in claim 3, further comprising a collection reservoir being connected to said casing pipe to receive fluid communication therefrom and connected to said production pipe to receive fluid communication therefrom.
 10. A method for optimally recovering hydrocarbon fluid from a well comprising: drilling a generally cylindrical borehole into a surface to the depth of a hydrocarbon producing zone therein, said borehole having a wall and a bottom; extending said borehole deeper than said hydrocarbon producing zone; introducing a casing pipe into said borehole, a portion of said casing pipe being perforated to allow hydrocarbon fluid to enter said casing pipe through said portion, said casing being generally cylindrical and having a smaller diameter than said borehole; filling the space between said casing pipe and the wall and bottom of said borehole with a filtering material, said filtering material extending from the bottom of said borehole up to a depth less than the depth of said hydrocarbon producing zone; and filling the remaining space between said casing pipe and the wall of said borehole with cement.
 11. A method for optimally recovering hydrocarbon fluid from a well, as recited in claim 10, further comprising pumping hydrocarbon fluid from the bottom of said casing pipe to a collection reservoir, said pumping step further comprising calculating the amount of petroleum that has been communicated through the traveling valve during said downstroke of said pumping cycle; and adjusting the speed of said traveling valve to a desired speed during the upstroke of said pumping cycle.
 12. A method for optimally recovering hydrocarbon fluid from a well, as recited in claim 10, further comprising pumping hydrocarbon fluid from the bottom of said casing pipe to a collection reservoir, said pumping step further comprising receiving the speed of a lift anchor driving said traveling valve throughout said downstroke; analyzing changes of speed of said lift anchor to determine the level of hydrocarbon fluid present in said well; and determining a desired speed of said lift anchor for transferring an optimal amount of petroleum during next the upstroke. adjusting the speed of said traveling valve to said desired speed during the upstroke of said pumping cycle. 